Scientists edit human embryo genes using more precise DNA technique

New research published this week marks a step forward in the ability to edit the genes of human embryos, using a technique called base editing that aims for greater precision than the CRISPR method that has long dominated the field.

Dieter Egli, an associate professor of developmental cell biology at Columbia University, and co-authors including Nathan Treff of Nucleus Genomics, a New York-based DNA-testing startup, said the technology could help fix disease-causing mutations in embryos. The research was published online Monday on a preprint server, meaning it has not yet undergone peer review.

“We’re not throwing the final ‘OK, you will have gene-edited babies tomorrow’ at the public,” Egli said. “That is a process that can occur through discussion matched with scientific progress.”

The technique the group used — base editing — allows researchers to target individual DNA letters in a sequence more precisely than CRISPR, which cuts out segments of DNA and can cause unintended damage when the wrong section is targeted. In 2018, Chinese scientist He Jianku said he used CRISPR to edit DNA in human embryos and was later imprisoned for the work.

Egli’s team focused on two genes — one linked to elevated risk of heart disease and another tied to blood disorders including sickle cell disease. In some cases, the research showed, they were able to edit both genes in the same embryo without unintended damage.

But the editing was not always complete. Nearly 80% of edited embryos became mosaics, meaning they ended up with a mix of edited and unedited cells. If those embryos developed into babies, they would still likely carry cells with the disease-causing mutations.

“I am generally supportive of the concept of embryo editing to prevent genetic disease,” said Dr. Paula Amato, a fertility expert at Oregon Health & Science University who was not involved in the research. She said the base editing method appears more promising than earlier techniques, but added that the mosaic issue needs to be resolved for the field to advance.

Base editing has been used in human embryos in prior peer-reviewed research, said Alexis Komor, an associate professor of biochemistry and molecular biophysics at the University of California, San Diego, who was not involved in the work. It was previously used to correct a disease-causing mutation and an Alzheimer’s disease-risk gene variant, Komor said.

“There really is not any unmet medical or clinical need for this, especially from an in vitro fertilization perspective,” Komor said. “Usually what you’ll hear is that they’re doing it just so that you know we can prevent genetic diseases, but there are so many other better ways to do that.”

Komor said she worries the research “is basically building a blueprint” for more ethically problematic forms of embryo editing. “In my opinion, I think this is a huge no-no,” she said. “There’s just no ethical way to use this.”

Creating gene-edited babies is illegal in the U.S. and many other countries. Scientists have long expressed concern that the technology could be used to promote eugenics.

The Dickey-Wicker amendment, which prohibits the use of federal funds for research on human embryos, limits National Institutes of Health funding for this line of work, said Glenn Cohen, a bioethicist and professor at Harvard Law School who was not involved in the research. Cohen said he believes the ban is “bad policy” but said it is unlikely to change.

Genomic Prediction, a New Jersey-based genetic-testing company that the researchers listed as a funder, was involved in the work, which was completed in June 2025. Treff worked at Genomic Prediction until August 2025 before joining Nucleus Genomics.

Nucleus Genomics CEO Kian Sadeghi said his company plans to fund further research by Egli building on the new findings. The company sells a polygenic embryo-screening product that produces risk scores for disease, as well as for factors such as height, IQ and eye color. The company has said the IQ predictions are limited in accuracy.

Sadeghi said base editing could one day be used in the IVF context to help parents avoid discarding embryos. “We see gene editing as an extension on this genetic-optimization stack,” he said, referring to the company’s embryo-screening business.